from The American Heritage® Dictionary of the English Language, 4th Edition
- adv. At what time: When will we leave?
- conj. At the time that: in the spring, when the snow melts.
- conj. As soon as: I'll call you when I get there.
- conj. Whenever: When the wind blows, all the doors rattle.
- conj. During the time at which; while: when I was young, I was sick all the time.
- conj. Whereas; although: She stopped short when she ought to have continued.
- conj. Considering that; if: How can he get good grades when he won't study?
- pro. What or which time: Since when has this been going on?
- n. The time or date: Have they decided the where and when?
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adv. Used to introduce questions about time.
- adv. Used to introduce indirect questions about time.
- conj. At what time.
- conj. At such time as.
- conj. As soon as.
- conj. At a time in the past,
- pro. What time; which time
- n. The time.
- interj. That's enough, a command to stop adding something, especially an ingredient of food or drink.
from the GNU version of the Collaborative International Dictionary of English
- adv. At what time; -- used interrogatively.
- adv. At what time; at, during, or after the time that; at or just after, the moment that; -- used relatively.
- adv. While; whereas; although; -- used in the manner of a conjunction to introduce a dependent adverbial sentence or clause, having a causal, conditional, or adversative relation to the principal proposition.
- adv. Which time; then; -- used elliptically as a noun.
from The Century Dictionary and Cyclopedia
- At what time? at which time?
- At the or any time that; at or just after the moment that; as soon as.
- At which time.
- At the same time that; whereas; while on the contrary: used adversatively, to denote contrast or incompatibility.
- When is often used as a quasi-pronoun, meaning ‘which time,’ introducing a dependent clause after since, till, or similar connective denoting time.
Middle English, from Old English hwenne.(American Heritage® Dictionary of the English Language, Fourth Edition)
From Middle English when(ne), whan(ne), from Old English hwenne, hwænne, hwonne ("when"), from Proto-Germanic *hwannē (“at what time, when”), from Proto-Indo-European *kʷo-, *kʷi- (“interrogative base”). Cognate with Dutch wanneer ("when") and wen ("when, if"), German wann ("when") and wenn ("when, if"), Gothic 𐍈𐌰𐌽 (ƕan, "when, how"), Latin quandō ("when"). More at who. (Wiktionary)